Electric heater terminal



June 17, 1941. N. MORRIS ELECTRIC HEATER TERMINAL Filed May 1, 1939 l f INVENToR.

4 @ZMLK/@aw @Zw/Vaio,

. ATTORNEY Patented June 17, 1941 ELECTREC HEATER TERRIINAL Nathan Morris, Silver Spring, Md., assigner to American Instrument Company, Silver Spring, Md., a copa-rtnersllip composed of William H. Reynolds and Leopold Freedman lipplicaticn May 1, 1939, Serial No. 271,204

5y Claims.

My invention relates broadly to electric heaters and more particularly to an improved construction of terminal for electric heaters having substantial protection against electrolysis.

`One of the objects of my invention is to provide a construction of terminal for electric heaters of the class in which a heating element is embedded in refractory within a, metallic tube adapted to be submerged in a fluid bath and wherein protective means are provided `abo-ut the heater terminal for preventing the entry of moisture into the refractory with subsequent electrolysis.

Another object of my invention is to provide a construction of electric heater terminal which permits the heater to be supported entirely through the terminal with minimum strain upon the parts of the terminal.

Still another object of my invention is to provide a construction of electric heater terminal in which a metallic shield is disposed about the end of the heater and provides a centering means for an insulator through which the connector extending to the heater wire extends to terminal means supported by the insulator.

A further object of my invention is to provide 'a construction of terminal for electric heaters in which the end of the tubular sheath enclosing the electric heater projects telescopically within a tubular member supported by an insulator which `is disposed centrally within a tubular metallic shield having a fluid-tight seal with the tubular metallic sheath and the tubular member `oiiering by their conjoint arrangement substantial protection to the electric heater against the decomposition eiiects of electrolysis.

Other and further objects of my invention reside in the construction of shielded termin-al for electric heaters as set forth more fully in the specification hereinafter following by reference to `the accompanying drawing, in which- Figure l is a front elevational view of an electric heater immersed in a bath and illustrating the manner of mechanically supporting the heater through the shielded terminals thereof, the view showing a fragmentary portion of a bath with a portion of the fluid container illustrated in section; Fig. 2 is an enlarged elevational View of the terminal with la portion of the tubular sheath which encloses the resistor broken away and shown in cross section and illustrating the portion of the resistor and electrical connector in side elevation; Fig. 3 is a vertical sectional view taken through Ithe electric heater terminal, moisture and vapor shield, sheath and resistor arrangement illustrated in Fig. 2; Fig. 4 is a transverse sectional view taken on line 4 4 oi Fig. 3; Fig. 5 is a transverse sectional view taken on line 5 5 of Fig. 3; and Fig. 6 is a transverse sectional view taken on line 6--6 of Fig. 3.

My invention is an improvement over the construction of electric heater terminal disclosed in William H. Reynolds Patent 1,969,760, dated August 14, 1934. In actual use of the terminal of the Reynolds patent it has been found that vapor from the bath in which the electric heater is employed tends to pass upwardly and attacks fthe molded parts of the terminal, gradually developing an annular crack between lthe molded parts so that the vapor works its way upwardly through the terminal until it forms a conducting deposit between the parts at diiierent potential W-hich often results in grounding of the electrical resistor, rendering the heater inoperative. Moreover, the moisture which creeps into the pants of the terminal enters the refractory between the sheath and the resistor resulting in decomposition of the resistor as a result of electrolysis. Upon grounding of the heater due to the conductive deposit resulting from the seepage of vapor :there is considerable possibility of shock to the operator.

The construction of my invention avoids the disadvantages encountered in the aforesaid construction and other `constructions of terminals. I provide a moisture `and vapor shield for the terminal end of the heater which serves as a supporting means for the heater, at the same time guarding against the seepage of fluid from the bath in which the heater is employed. The tubular sheath which encloses the electric resistor embedded within refractory insulation is received telescopically within the end of a tubular member which projects from an insulation member. The tubular sheath of the heater and the tubular member are coextensive for substantial distance adjacent the ends thereof. The moisture and vapor shield surrounds the tubular member and extends about the insulated member into which the tubular member and tubular sheath extend. The shield is soldered, brazed or welded to the tubular sheath and tubular member forming a huid-.tight joint so that seepage of moisture is absolutely prevented. The exterior of the shield is screw threaded to receive nuts that engage the exterior of the shield and clamp on opposite sides of any suitable support. The shield is of sturdy construction so that the entire weight of the heater may be directly supported through the shield. The resistor is electrically connected through a connector which extends through the insulator and is connected to a terminal carried by the insulator.

The construction of electric terminal herein set forth has been found to be highly practical in manufacture and successful in use.

Referring to the drawing in more detail, reference character I designates the electrical resistor which is coiled or wound and embedded within the refractory insulation 2 within tubular sheath 3. A metallic sleeve I or electrical connector is slid over the end of the resistance wire I and clamped in position with respect thereto as indicated at 5, forming a good electrical connection therewith. 'Ilhe sleeve or connector extends upwardly through the refractory 2 and beyond the end of tubular sheath 3 and through bore 6 in tubular insulator 'I and into the aX- ially extending bore 8 of terminal member 9 carried by tubular insulator 'I. The terminal member 9 is screw threaded at II) to receive the binding post I2 for securing any suitable electrical conductor I4 in position with respect thereto.

The tubular insulator I has a tubular member I5 extending downwardly therefrom in a position to receive the end of the tubular sheath 3. Tubular member I5 vand tubular sheath 3 are coextensive for a substantial distance and have a tight interengagement so that seepage of moisture therebetween is practically impossible. The moisture and vapor shield for the electric terminal is shown at I5 surrounding the tubular insulator I and tapering therefrom to a Zone adjacent the end of the tubular member I5. The shield I6 is partially cylindrical throughout the upper portion of its length and is somewhat truste-conical throughout the lower portion of its length, terminating in an annular cylindrical zone II forming a tight interengagement with the end of tubular member I5 at the zone indicated at I3. 'Ihe shield I6 and the end of tubular member I5 are soldered, bra-Zed or welded to the exterior surface of sheath 3 by an annular joint represented at I9 for preventing seepage of moisture and avoiding entrance of moisture into the refractory material 2 through the upper end of sheath 3, thereby preventing electrolysis and decomposition of the resistor or connector associated therewith.

The exterior of the moisture and vapor shield I6 is screw threaded along its upper cylindrical portion as represented at 20. The screw threaded cylindrical portion 2D passes through aperture 23a. in plate 23 and is engaged by nuts 2I and 22 adapted to grip opposite sides of the plate 23 for supporting a heater'in position. A separate bracket is not necessary as the electric heater `may be directly supported by a cover plate extending over the container represented in section at 24 in Fig. 1, whereby the electric heateris suspended in the bath 25. Because of the protection afforded to the electrical terminal by means of the shield at the upper end of the heater,'see-page of moisture into the insulator 'I and into the refactory 2 is prevented so that decomposition resulting from electrolysis is avoided. The electric heater is considerably strengthened by the construction of shield at the end of the tubular sheath thereby increasing the life and usefulness of the electric heater.

I have shown the heater arranged in a vertical position with respect to a bath. However,

I desire that it-be understood that the heater constructionA of my invention may be readilyv employed in a horizontal position below the fluid line of a tank. Where the heater is submerged and used in a horizontal position, I may employ deformable gaskets such as lead washers intermediate the nuts 2I and 22 and the Wall of the tank to effect a liquid-tight seal. The substantial seal provided at I9 between shield I6 and tubular member I5 and between tubular member I5 and the sheath 3 insures against seepage of moisture into the refractory material 2 even under conditions where the heater is submerged horizontally in the tank.

While I have described my invention in one of its preferred embodiments, I desire that it be understood that modifications may be made and no limitations upon my invention are intended other than maybe imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In an electric heater of the embedded resistor type, in combination, a refractory filled sheath-like enclosure, an insulator recessed at one end thereof to support an electric terminal and recessed 'at the opposite end thereof to receive a tubular member, said sheath-like enclosure extending telescopically into said tubular member, a moisture and vapor shield surrounding said insulator in surface contact therewith and extending to a position adjacent the end of said tubular member, a moisture and vapor seal between said shield and said tubular sheath-like enclosure at the end of said tubular member, and means for mechanically supporting said tubular sheath-like enclosure through said shield.

2. In an electric heater of the embedded resistor type, in combination, a refractory lled tubular sheath-like container, a cylindrical insulator, a sleeve-like member projecting from said insulator for receiving the end of said tubular sheath-like container, an electric terminal supported by said insulator, a shield surrounding said insulator and terminating substantially at the terminus of said sleeve-like member, a moisture and vapor seal between the sheath-like container and the end of said shield at the end of said sleeve-like member, said shield being substantially cylindrical and of suitable diameter throughout the portion which surrounds said insulator for laterally supporting said insulator and tapering from said portion to la position adjacent the junction of the shield with said sleeve-like member, and means for wholly supporting said tubular sheath-like container through said shield.

3. A shielded terminal for an'electric heater of the embedded resistor type co-mprising in cornbination with a refractory filled tubular sheathlike container, a cylindrical insulator connected with the end of said container and constituting a primary closure for said refractory filled container, a moisture and vapor shield having a substantially cylindrical sleeve portion surrounding said insulator land an extended substantially frusto-conical portion terminating in connection with said container, a moisture and vapor seal at the junction of said shield and said container, said shield and said seal constituting a secondary closure for said container effective absolutely to exclude moisture and vapor from the interior of said refractory filled container, and an electric terminal carried by said insulator.

4. A terminal as set forth in claim 3 wherein said shield is screw threaded interiorly in the cylindrical sleeve portion thereof, and including means engaged with the screw threaded sleeve portion of said shield for supporting said terminal and thereby the electric heater.

5. A shielded terminal for an electric heater of the embedded resistor type comprising, in combination with a refractory lled casing, an insulator, a tubular member embedded for a portion of is length in one end of said insulator and having a portion projecting outwardly therefrom to t about said casing, said tubular member having a flared mouth at its outer end whereby the tubular member may be fitted about an end of said casing and rmly secured to said casing by solder disposed about the Leasing and extending into the flared mouth oi said tubular member, an electric terminal post embedded in the opposite end or" said insulator in alignment with said tubular member, said insulator having a bore between the inner ends of said terminal post and said tubular member, a. conductor having an end portion passed through sai-d tubular member and said insulator and having a contact engagement with said terminal post, said insulator constituting a closure for said refractory lled casing with said bore therein being provided for said conductor, a shield member engaged with the exterior of said insulator and extending in the direction of said tubular member, said shield member being tapered to engage said tubular member substantially at the flared mouth of said tubular member, and a solder seal disposed at the junction of said shield and said tubular member and extending into the flared mouth of said tubular member for firmly securing not only said tubular member to said casing but also said shield member to said tubular member, said shield member being in sealed relation to said casing and effective to exclude moisture and vapor from the connection of said tubular member and said insulator, said shield also constituting means whereby said heater may be supported.

NATHAN MORRIS. 

